cerebras · text

Step-3.5-Flash-REAP-121B-A11B

cerebras/Step-3.5-Flash-REAP-121B-A11B

Step-3.5-Flash-REAP-121B-A11B at I1-IQ1_S is exactly 24,414,167,744 bytes (22.74 GiB / 24.41 GB) — an effective 1.615 bits per weight, not the nominal 1. Its KV cache at 32K is 13.03 GiB, not the 45.00 GiB a flat formula predicts.

From the file· summed from 1 file(s)From the file· KV per layer
Parameters
121B
Architecture
step35
45 layers
Context
262,144
native (config.json)
License
other

Shipped quantizations

● exact bytes, summed from published files
QuantSize●Exact bytes●Effective bpw●Tensors●Publisher
I1-IQ1_S22.74 GiB24,414,167,7441.615—mradermacher
I1-IQ1_M25.28 GiB27,146,462,9121.795—mradermacher
I1-IQ2_XXS29.52 GiB31,700,288,1922.096—mradermacher
I1-IQ2_XS32.98 GiB35,407,835,8402.342—mradermacher
I1-IQ2_S33.40 GiB35,858,358,9762.371—mradermacher
I1-IQ2_M36.79 GiB39,501,419,2002.612—mradermacher
I1-Q2_K_S37.79 GiB40,572,452,5442.683—mradermacher
I1-Q2_K41.19 GiB44,227,395,2642.925—mradermacher
I1-IQ3_XXS43.40 GiB46,597,518,0163.082—mradermacher
I1-IQ3_XS45.92 GiB49,308,838,5923.261—mradermacher
I1-Q3_K_S48.71 GiB52,297,181,8883.459—mradermacher
I1-IQ3_S48.73 GiB52,322,249,4083.460—mradermacher
I1-IQ3_M49.23 GiB52,857,023,1683.496—mradermacher
I1-Q3_K_M53.75 GiB57,715,993,2803.817—mradermacher
I1-Q3_K_L58.48 GiB62,791,625,4084.153—mradermacher
I1-IQ4_XS60.12 GiB64,555,701,9524.269—mradermacher
I1-Q4_063.71 GiB68,411,672,2564.524—mradermacher
I1-Q4_K_S63.83 GiB68,536,452,8004.533—mradermacher
I1-Q4_K_M67.82 GiB72,817,116,8644.816—mradermacher
I1-Q4_170.61 GiB75,814,545,0885.014—mradermacher
I1-Q5_K_S77.62 GiB83,340,101,3125.512—mradermacher
I1-Q5_K_M79.79 GiB85,672,773,3125.666—mradermacher
I1-Q6_K92.51 GiB99,331,908,2886.569—mradermacher

KV cache by context

computed per layer — this model uses sliding-window attention
ContextKV cache (f16)●Flat formulaOverstated byFull / windowed / recurrent
4,0962.53 GiB5.63 GiB2.22×12 / 33 / 0
8,1924.03 GiB11.25 GiB2.79×12 / 33 / 0
16,3847.03 GiB22.50 GiB3.20×12 / 33 / 0
32,76813.03 GiB45.00 GiB3.45×12 / 33 / 0
65,53625.03 GiB90.00 GiB3.60×12 / 33 / 0
131,07249.03 GiB180.00 GiB3.67×12 / 33 / 0

33 of 45 layers cache only a 512-token window rather than the full context, on a period of . Figures assume the default configuration; --swa-full disables the saving entirely.

Compare with

same modality, comparable size
vs Qwen3-Coder-30B-A3B-Instructvs Qwen3.6-27Bvs Qwen3.8-27Bvs gemma-4-E4B-itvs Qwen3-30B-A3B-Thinking-2507vs Qwen3-8BAll alternatives →Will it fit on my card? →

Will it run on your card?

full quant x context sweep
By VRAM:8GB12GB16GB24GB32GB48GB
Radeon RX 6500 XT 4GBGeForce RTX 3050 6GBGeForce RTX 5050 8GBGeForce RTX 3080 10GBGeForce RTX 2080 Ti 11GBGeForce RTX 5070 12GBGeForce RTX 5060 Ti 16GBApple M3 Pro 18GBGeForce RTX 3080 Ti 20GBGeForce RTX 5090 D V2 24GBGeForce RTX 5090 D 32GBApple M5 Max 36GBApple M5 Pro 48GBApple M5 Max 64GBApple M3 Ultra 96GBApple M5 Max 128GBApple M2 Ultra 192GBApple M3 Ultra 256GBApple M3 Ultra 512GB

Why other calculators give a different number

A parameters × bits ÷ 8 estimate puts I1-IQ1_S at roughly 63.37 GiB. The real file is 22.74 GiB, because a quantization is a mixture and some tensors are always kept at higher precision. The larger discrepancy is the cache: a flat formula gives 45.00 GiB at 32K context where the real figure is 13.03 GiB, because most of this model's layers cache a fixed window rather than the whole context.

Architecture

from config.json
Layers
45
Attention heads
64
KV heads
64
Head dim
128
Hidden size
4096
Vocab
128,896
Sliding window
512
SWA period
—
MLA
no
Experts
—
Experts per token
—
use_sliding_window
—

Questions people ask

How much VRAM does Step-3.5-Flash-REAP-121B-A11B need?
I1-IQ1_S is exactly 24,414,167,744 bytes (22.74 GiB) in weights. Add the KV cache, which depends on your context length, plus roughly half a gigabyte of runtime overhead.
How large is Step-3.5-Flash-REAP-121B-A11B's KV cache?
13.03 GiB at 32K context with an f16 cache, computed per layer. Quantizing the cache to q8_0 roughly halves it, which is often the difference between a context length fitting and not.
Which quantization of Step-3.5-Flash-REAP-121B-A11B should I use?
Q4_K_M is the usual default. Pick the largest quantization that fits your card at the context you actually need — the table above gives exact sizes for every one published.